Sealing and packaging device for cover film on tray

ABSTRACT

The present invention heat-seals a cover film onto a tray accommodating an item to be packaged, without creating wrinkles in the film. In the present invention, respective touch bars provided at equidistant intervals on chains respectively and continuously move trays accommodating items to be packaged, and a frame to which sealers of the same outline as the trays are fixed moves back and forth at the same speed, in the same direction as the trays. A crank below the frame moving back and forth raises a sealing base frame upwards when the frame advances, the trays are pushed against the sealers positioned above the same, via the moving film, and the film is welded to the open edge of the trays. The movement of the sealing base frame is a box motion, and the efficiency of the sealing operation is increased.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sealing and packaging device, whereinrespective individual trays disposed at equidistant intervals in acolumn fashion, and band-shaped cover film for covering these respectivetrays, are moved and conveyed at the same speed on a conveyor line, theband-shaped cover film being welded successively to an edge flangeportion of each tray.

2. Description of the Related Art

In what are commonly known as tray packaging machines, conventionally,there have existed devices having a structure wherein individual traysfor respectively accommodating items to be packaged are disposed in aplurality of mould frames supported at equidistant intervals on anendless chain, these trays being conveyed along an endless path in aunified manner with the chain, while band-shaped cover film is fed overeach of the trays, the film furthermore being welded to a flange portionat the edges of each tray, by means of a heating frame which descendsfrom above. A merit is obtained in that the packaged item output by thepackaging machine emphasizes the freshness of the food productaccommodated in the tray, due to the transparency of the cover filmwhich is attached horizontally to the upper face of each tray. However,if the packaged item is accommodated in the tray in a mounded fashion,then a problem arises in that the cover film covering same will bedeformed into a bulging shape and will create a plurality of pleats.

U.S. Pat. No. 6,488,972 discloses a device which does not form pleats inthe cover film. As illustrated in FIG. 16, U.S. Pat. No. 6,488,972 is areference which relates to a device wherein an endless stretching frame102 is pressed down about the perimeter of an item to be packaged 101,which is accommodated in a mounded fashion in a tray 100, and is pressedagainst the tray 100 while stretching the stretch film 103 against theresistance of the item to be packaged 101, in addition to which, thefilm 103 is welded to a flange on the perimeter edge of the tray bymeans of a heat sealer (sealing frame) disposed around the periphery ofthe stretching frame 102. The packaging machine described in thisreference does have a merit in that pleating of the cover film iseliminated. However, when the stretch film 103 is stretched by thestretching frame 102, since the stretching frame 102 stretches the film103 by means of friction, a plurality of wrinkles 104 are generated as asecondary effect in the portion of the film about the frame 102 which isnot stretched. Consequently, this wrinkled portion becomes welded to thetray 100 by the heat sealer. Therefore, a problem arises in that thewrinkled portion 104 is liable to peel away from the tray 100, due tothe elastic restoring force of the film that has been stretched.

SUMMARY OF THE INVENTION

The object of the present invention is to weld the film without formingwrinkles about the perimeter of the tray, when an item to be packagedwhich is accommodated in a mounded fashion in a tray is hermeticallypackaged by means of cover film. In other words, the present inventionis suitable for the efficient hermetic packaging of block type items tobe packaged, which stand up above a tray, without forming wrinkles inthe cover film.

The present invention comprises: means for moving touch bars provided atequidistant intervals and spanning between endless chains in respectiveside positions, in a unified manner with the chains, and pushing andadvancing respective trays along the upper face of a horizontalconveyance path, at equidistant intervals in a column fashion, by meansof the respective touch bars; a general frame moving back and forthreciprocally in the same direction as the touch bars, in a cutawayregion in an intermediate part of the conveyance path; bridge platesfixed to the general frame and moving back and forth reciprocally in aunified manner with the general frame, within the cutaway region at thesame height as the face of the conveyance path; a lifting mechanism formoving a sealing base frame disposed surrounding the bridge plates,upwards and downwards, about the periphery of the bridge plates, inresponse to the reciprocal movement of the frame; sealers fixed to thegeneral frame above the sealing base frame and having the same outlineas the open edge of the tray supported on the sealing base; and a filmconveyance mechanism for moving a band-shaped film between the sealersand the bridge plates, in the same direction as the touch bars; beingcomposed in such a manner that, when the lifting mechanism performs anupward movement, the band-shaped film is pressed by the sealing baseframe against film pushing elements disposed in isolated fashion aboutthe periphery of the sealers, and, with further upward movement of thelifting mechanism, the band-shaped film is pressed against the sealersand welded by same at the open edge of the trays placed on the sealingbase, while the band-shaped film is pushed upwards by a to-be-packageditem accommodated in the tray in a mounded fashion, and furthermore, theband-shaped film is pressed against endless blades surrounding theperiphery of the sealers and is cut out in accordance with the outlinesof the trays.

Moreover, the present invention comprises: means for moving touch barsprovided at equidistant intervals and spanning between endless chains inrespective side positions, in a unified manner with the chains, andpushing and advancing respective trays along the upper face of ahorizontal conveyance path, at equidistant intervals in a columnfashion, by means of the respective touch bars; a general frame providedin a fixed manner in a cutaway region in an intermediate part of theconveyance path; bridge plates provided in a fixed manner on the generalframe within the cutaway region at the same height as the face of theconveyance path; a lifting mechanism for moving a sealing base framedisposed surrounding the bridge plates, upwards and downwards; sealersfixed to the general frame above the sealing base frame and having thesame outline as the open edge of the trays supported on the sealingbase; and a film conveyance mechanism for causing a band-shaped film tomove between the sealers and the bridge plates, intermittently, in thesame direction as the touch bars.

In U.S. Pat. No. 6,488,972, described above, since stretch film ispressed against a tray while being stretched by a stretching frame abouta to-be-packaged item accommodated in a mounded fashion in the tray, awrinkled section occurring at the periphery of the endless frame iswelded to the tray by the heating frame, but in the present invention,since the portion to the inner side of pushing elements, where wrinklesare not liable to occur, is welded, occurrences such as peeling off ofthe welded section due to wrinkling are eliminated, and exposure of thepackaged item to the air is prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a device according to the present invention;

FIG. 2 is a plan view of the device according to the present invention;

FIG. 3 is a front view of the device according to the present invention;

FIG. 4 is a partial enlarged side view of the device according to thepresent invention;

FIG. 5 is an action diagram relating to the previous diagram;

FIG. 6 is an enlarged side view of a sealing base;

FIG. 7 is a diagram for describing the action of the sealing base;

FIG. 8 is a partial oblique view of a general frame;

FIG. 9 is a diagram for describing the action of a sealing mechanism;

FIG. 10 is a partial front view of the device according to the presentinvention;

FIG. 11 is a plan view of a device for removing wrinkles in the film;

FIG. 12 is an enlarged front view of the rollers;

FIG. 13 is a diagram for describing the movement of each member of thedevice;

FIG. 14 is a diagram for describing movement of each member of a deviceaccording to a second embodiment;

FIG. 15 is a side view of a device according to a third embodiment; and

FIG. 16 is an illustrative diagram of a prior art example.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention achieves a composition whereby a cover film isheld in such a manner that pleats are formed outside the perimeter edgeof a tray, rather than inside the perimeter edge thereof, and the filmis welded to the tray on the inner side of the held portion.

Embodiment 1

Touch bars 12 supported at equidistant intervals on endless chains 13push and advance trays 10, at equidistant intervals, along the upperface of the horizontal conveyance path 11 in FIG. 1. More specifically,two path of travel plates 11 a for the purpose of a conveyance path aredisposed on stays 14 which are provided spanning between a pair of sideplates 32 provided at respective side positions, as illustrated in FIG.2, and a pair of endless chains 13 are disposed on either side of thisconveyance path, the touch bars 12 being provided spanning between theendless chains 13. The trays 10 are caused to perform sliding movementover the path of travel plates 11 a, by means of the touch bars 12spanned between the two chains.

A cutaway region 15 is formed in an intermediate part of the conveyancepath 11, and a general frame 16 disposed so as to extend through thisregion is capable of reciprocal movement along side rails 70 disposed atrespective side positions.

In the general frame 16 in FIG. 1, pillar members 17 are installed in astanding manner in four respective corners, the upper and lower parts ofthe pillar members 17 being fixed respectively to a top plate 18 and abottom plate 19, and the intermediate parts thereof being fixed to anintermediate plate 20. Moreover, a screw bar 23 having a large lead issupported between a pair of bearings 22, 22 fixed to a continuousimmobile machine platform 21, and the screw bar 23 is screwed into afemale screw block 24 fixed to the intermediate plate 20 of the generalframe. A composition is adopted whereby, by forward or reverse rotationof a servo motor 25 which is coupled to one end of the screw bar 23, thescrew bar 23 is caused to rotate and the female screw block 24 is causedto move, in such a manner that the general frame 16 performs forward andbackward movement. Bridge plates 27 are provided on a plurality of legs26 erected in a standing fashion on the intermediate plate 20, at thesame height as the conveyance path 11 (for further detail, see FIG. 6).

FIG. 8 is a partial oblique view of the general frame 16 describedpreviously, wherein two bridge plates 27 are fixed in a mutuallyparallel fashion by means of legs 26 on an intermediate plate 20 whichis fixed to the pillar members 17 in the four corners, and a sealingbase frame 28 is installed in a state whereby it makes contact with theperimeter of the bridge plates 27. If it is supposed that trays 10 aremounted on the bridge plates 27, then these trays 10 can be pressedupwards while being supported by the sealing base frame 28, by a forcein the vertical direction which acts on pins 31 in the side faces of thebed frame 28. A crank 34 which is turned by a motor 33 as illustrated inthe lower portion of FIG. 1 forms a shift mechanism for causing upwardand downward movement of the sealing base frame 28 in the upper portion,by means of con rods 40, via the pin 31.

The sealing base frame 28 shown in FIG. 2 is also provided with a rimwhich receives two trays in a parallel fashion. Extendable andcontractable transfer regions 36 having a finger shape which slidebetween a plurality of bars 35 of the same finger shape fixed to thepath of travel plates 11 a are respectively supported at the front andthe rear of the general frame 16. Therefore, when the general frame 16performs reciprocal movement, the trays 10 pushed by the touch bars 12pass from the conveyance path 11, over the extending and contractingtransfer regions 36, and are transferred onto the bridge plates 27inside the seal base plate 28, upon which it becomes possible for themto be ejected from the bridge plates 27.

The general frame 16, which is illustrated from a different direction inFIG. 3, moves back and forth along the two side rails 70 due to therotation of the screw bar 23, as described previously. On the otherhand, the motive force transmitted from the motor 33 to the crank 34causes the sealing base frame 28 to move upwards and downwards, by meansof the con rods 40. Moreover, in the general frame 16, two sealers 38having the same profile as the open edge of the trays 10 are supportedand arranged respectively in the regions above the two bridge plates 27.

The sealers 38, which have an inverted bowl shape, as illustrated inenlarged view in FIG. 4, connect with the lower ends of a plurality ofspindles 44 supported slidably on a two-stage upper section fixed plate30. Furthermore, elastic resistance members 45 respectively formed bycoil springs are disposed about each of the spindles 44. Moreover, aplurality of rod members 47 are suspended movably in the verticaldirection, from the fixed plate 30, in such a manner that they connectwith the perimeters of the sealers 38, a rubber block 46 being providedrespectively on the lower end of each of the rod members 47, therebyforming film pushing elements. An endless blade 50 is installed on theinner side of each of the pushing elements 46, and continuous grooves 51are formed on the upper face of the lower sealing base frame 28, in sucha manner that the endless blades 50 can be inserted into same.

On the other hand, a band-shaped film 41 disposed over the conveyancepath 11 and following same is moved at the same speed as the chains 13,by the winding movement of a reel 42, and the speed of advance of thegeneral frame 16 is also the same as the speed of the film 41.

The intermediate plate 20 of the general frame in FIG. 6 performsreciprocal movement in the direction of the arrows 53, 54, inassociation with the bridge plates 27. At the time when the movement ofthe intermediate plate 20 reaches the end section of the arrow 54, thetouch bar 12 causes the trays 10 to move from the conveyance path 11 tothe bridge plates 27, and, at that instant, the chains 13 halttemporarily. Immediately thereafter, the movement of the intermediateplate 20 changes to the direction of arrow 53, as illustrated in FIG. 7,and, simultaneously, the sealing base frame 28 starts to rise up, as thearrow 55 indicates, between the touch bar 12 and the bridge plates 27,and the chains 13 start operation again in such a manner that theintermediate plate 20 is advanced. The sealing base frame 28 is movedfurther upwards during this action, and, by supporting the rim portion56 at the perimeter edge of the tray 10, it pushes the item to bepackaged 52, provided in a mounded fashion rising above the tray 10,towards the band-shaped film 41.

Due to further raising (as indicated by the arrow) of the sealing baseframe 28 illustrated in FIG. 5, the sealing base frame 28 compresses aspring 48 provided above each of the pushing elements 46, and the filmat the periphery of the tray 10 is held between the sealing base frame28 and the pushing elements 46, while the film 41 is held under pressurebetween the sealers 38 and the sealing base frame 28 by means of thereaction force of the elastic resistance members 45. In this case, sincethe sealers 38 are heated by thermoelectric wiring 72, the film 41 ispressed against the rim portion 56 of the open edge of the tray 10 andis welded to same. Thereupon, the endless blades 50 which insert intothe grooves 51 cut out the film 41 along the outline of the tray 10.

As a result of the sealers 38, which are partially illustrated in FIG.9, moving back and forth constantly in the direction of the arrows 53,54, and of the seal base 28 moving upwards and downwards constantly, theseal base 28 performs a box motion operation as illustrated by thedotted line 60 in the diagrams, due to the combined action of these twomovements.

FIG. 13 shows the sequences of the respective movements of the generalframe 16 and the band-shaped film 41 described previously, as well asthe sealing base frame 28 and the touch bar 12. In other words, theband-shaped film 41 always performs a forward movement at a uniformspeed, whereas the general frame 16 repeats a reciprocal movement ofadvance and retreat over a prescribed area. At the same time, thesealing base frame 28 repeats a raising and lowering motion, in orderthat it performs a box motion operation together with the reciprocalmovement of the general frame 16. The touch bars 12 advance constantly,but they halt temporarily, only while the sealing base frame 28 israised, in such a manner that they do not interfere with the movement ofthe sealing base frame.

Therefore, as the sealing base frame 28 and the sealers 38 performreciprocal movement following the band-shaped film 41 and trays 10 whichmove in the direction of the arrow 53 in FIG. 5, packaging operationsare successively repeated, but when an item to be packaged 52 which isin a mounded state pushes upwards on the band-shaped film 41, a wave isapplied unavoidably to that film 41. However, the portion where thesealer 38 presses down against the band-shaped film 41 does not lie inthe region containing a large number of small pleats situated on theouter side of the pushing elements 46, but rather, it lies to the insideof the pushing elements 46, and hence there are relatively few wrinklesin the film that is welded to the rim portion 56 of the tray 10.

As shown in FIG. 10, in the detailed composition of the rollers 61, 62disposed to the rear of the general frame 16 in FIG. 1, the two sideedges of the band-shaped film 41 are respectively held between pairs ofupper and lower driving rollers 61, 62, and these rollers are supportedand arranged on an immobile machine platform 21, that is different tothe general frame 16 which is constantly being displaced, in otherwords, they are supported on the machine platform 63 of the device.

Moreover, as shown in FIG. 11, the rollers 61, 62 on either side aredisposed at an inclined angle in such a manner that the band-shaped film41 is tensioned towards either side, in the direction of travel thereof(arrow 64). In other words, the rollers 61, 62 are positioned at anangle of inclination which is suitable for directing the film 41 in thedirections of the arrows 65. Furthermore, these directing rollers 61, 62are each provided internally with a one-way clutch which permits therollers 61, 62 to perform free rotation only in the direction of travel64 of the band-shaped film 41. Although the film 41 loses tensioningeffects in the lateral directions due to the cutaway holes 66 of thefilm that have been cut out in the previous step, and althoughdistortion occurs in the film 41, giving rise to wrinkles, in thevicinity of the cutaway holes 66 on the forward side of the sealing baseframe 28 in the direction of travel 64, since the rollers 61, 62situated at this position do not turn in the reverse direction, the film41 is pulled and tensioned in the direction of either side only, andhence the generation of wrinkles in the film 41 welded to the tray 10 isprevented in advance.

FIG. 12 shows a guide 67 which supports the respective rollers 61, 62,the axle of the lower roller 62 being supported on the guide 67 in sucha manner that it cannot be displaced in the upward or downwarddirection, whereas the upper roller 61 is able to be displaced upwardsor downwards along the guide 67, the both rollers 61, 62 holding thefilm 41 under pressure between them constantly due to the reaction forceof a coil spring 68, and, by releasing a pressure contact element 71 inthe direction of the arrow, taking the pin 69 as an axis, it is possibleto create a gap between both rollers 61, 62 and thereby to facilitatethe insertion of the film 41 therebetween.

Second Embodiment

A second embodiment has a composition wherein the respective membersillustrated in FIG. 14 are caused to operate as illustrated in thediagram. In other words, a general frame 16 repeats reciprocal movementof advancing and retreating through a prescribed area. A sealing baseframe 28 performs a box motion operation, in association with thereciprocal movement of the general frame 16, and hence it repeats risingand descending movements. The touch bars 12 advance constantly, but theyare temporarily caused to retreat backwards a little in such a mannerthat they do not interfere with the rising of the sealing base frame 28.The film 41 constantly performs forward movement at a uniform speed, butit halts temporarily only when the sealing base frame 28 is raised frombelow.

Third Embodiment

FIG. 15 shows a device according to a third embodiment. The compositionof this third embodiment is such that a general frame 16 provided in acutaway region 15 in an intermediate part of the conveyance path 11 isfixed and does not perform reciprocal movement. Therefore, the femalescrew block 24, screw bar 23, servo motor 25, finger shaped bars 35 andtransfer regions 36, and the like, are not provided, but since the basiccomposition is the same, the same reference numerals are used anddetailed description thereof is omitted here.

In this third embodiment, touch bars 12 performing intermittent movementpush respective trays 10 on a conveyance path 11 and advance same ontobridge plates 27 which are fixed to a general frame 16. In order toavoid collision between the touch bar 12 and the sealing base frame 28which rises upwards, the touch bar 12 is temporarily caused to retreatbackwards. When the sealing base frame 28 is raised upwards by thelifting mechanism, then the band-shaped film 41 is temporarily halted.Therefore, the band-shaped film 41 moves in an intermittent fashion.While the band-shaped film 41 is temporarily halted, the sealing baseframe 28 is raised up, and by supporting a rim portion 56 at theperimeter edge of the tray 10, it pushes the item to be packaged 52,which is positioned in a mounded state in the tray, upwards in thedirection of the band-shaped film 41. Thereupon, the film 41 is pressedagainst and welded to the rim portion 56 of the open edge of the tray10, and endless blades 50 cut the film 41 along the outline of the tray10.

What is claimed is:
 1. A device for sealing and packaging cover filmonto a tray having open edge and accommodating an item in a moundedfashion, comprising: a pair of endless chains; a plurality of touch barsspanning between the endless chains at equidistant intervals; means formoving the endless chains and the touch bars in unison for pushing andadvancing respective trays disposed in said equidistant intervals alongan upper surface of a horizontal conveyance path; a general frame movingback and forth reciprocally in a parallel direction with said touch barsand in a defined region of said conveyance path; bridge plates fixed tosaid general frame for moving back and forth reciprocally in unison withsaid general frame in said defined region and at the same height as theupper surface of said conveyance path; a sealing base frame disposedsurrounding said bridge plates for supporting the open edge of the tray;a lifting mechanism for moving said sealing base frame upwards anddownwards about the periphery of said bridge plates in response to thereciprocal movement of said frame; sealers fixed to said general frameabove said sealing base frame and having the same outline as the openedge of the tray supported on said sealing base frame; a film conveyancemechanism for moving a band-shaped film between said sealers and saidbridge plates, in the same direction as said touch bars; a film pushingelement disposed in an isolated fashion about a periphery of saidsealers; and an endless blade having the same outline as the outline ofthe tray and disposed surrounding the periphery of said sealers;wherein, when said lifting mechanism performs an upward movement, saidband-shaped film is pressed by said sealing base frame against filmpushing elements, and with further upward movement of the liftingmechanism, said band-shaped film is pressed against and welded by saidsealers to the open edge of the tray supported on said sealing base,while said band-shaped film is pushed upwards by a to-be-packaged itemaccommodated in said tray in said mounded fashion, and furthermore, saidband-shaped film is pressed against said endless blade and is cut out inaccordance with the outline of said tray.
 2. The device for sealing andpackaging cover film onto a tray according to claim 1, furthercomprising pairs of cooperating upper and lower directing rollers forgripping respective side edges of the band-shaped film; wherein saidpairs of rollers are supported and arranged on an immobile machineplatform differing from the general frame at respective sides downstreamof said sealing base frame, these rollers on either side being arrangedat an inclined angle in such a manner that said band-shaped film istensioned towards said either side, in the direction of travel thereof;and wherein, a one-way clutch whereby each roller is able to performfree rotation only in the direction of travel of said band-shaped filmis disposed inside each of the directing rollers.
 3. The device forsealing and packaging cover film onto a tray according to claim 1,further comprising upstream transfer fingers and downstream transferfingers disposed in said defined region of the conveyance path, whereinsaid transfer fingers are configured to extend and contract inaccordance with the reciprocal movement of said general frame totransfer said trays from said conveyance path upstream of the generalframe to said bridge plates and from said bridge plates to saidconveyance path downstream of the general frame.
 4. The device forsealing and packaging cover film onto a tray according to claim 1,wherein the movement of the touch bars at the moment that the sealingbase frame is pushed up towards the sealers is halted temporarily whilesaid sealing base frame is raised up above said touch bars.
 5. Thedevice for sealing and packaging cover film onto a tray according toclaim 1, wherein the film is temporarily halted and the touch bars aretemporarily caused to retreat, at the moment that the sealing base frameis pushed up towards the sealers.
 6. A device for sealing and packagingcover film onto a tray having open edge and accommodating an item in amounded fashion, comprising: a pair of endless chains; a plurality oftouch bars spanning between the endless chains at equidistant intervals;means for moving the endless chains and the touch bars in unison forpushing and advancing respective trays disposed in said equidistantintervals along an upper surface of a horizontal conveyance path; ageneral frame fixed in a defined region of said conveyance path; bridgeplates fixed on said general frame in said defined region and at thesame height as the upper surface of said conveyance path; a sealing baseframe disposed surrounding said bridge plates for supporting the openedge of the tray; a lifting mechanism for moving said sealing base frameupwards and downwards about the periphery of said bridge plates; sealersfixed to said general frame above said sealing base frame and having thesame outline as the open edge of the tray supported on said sealing baseframe; a film conveyance mechanism for moving a band-shaped film betweensaid sealers and said bridge plates, in the same direction as said touchbars; a film pushing element disposed in an isolated fashion about aperiphery of said sealers; and an endless blade having the same outlineas the outline of the tray and disposed surrounding the periphery ofsaid sealers; wherein, when said lifting mechanism performs an upwardmovement, said band-shaped film is pressed by said sealing base frameagainst film pushing elements, and with further upward movement of thelifting mechanism, said band-shaped film is pressed against and weldedby said sealers to the open edge of the tray supported on said sealingbase, while said band-shaped film is pushed upwards by a to-be-packageditem accommodated in said tray in said mounded fashion, and furthermore,said band-shaped film is pressed against said endless blade and is cutout in accordance with the outline of said tray.
 7. The device accordingto claim 6, wherein the touch bars are caused temporarily to retreat atthe moment that the sealing base frame is pushed upwards towards thesealers, thereby avoiding collision between the touch bars and thesealing base frame.